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Andrew I Cooper

Publications and source records attributed to Andrew I Cooper.

10 recordsLinked to original sources
PubMed2007

Design of polymeric stabilizers for size-controlled synthesis of monodisperse gold nanoparticles in water.

A new methodology is described for the one-step aqueous preparation of highly monodisperse gold nanoparticles with diameters below 5 nm using thioether- and thiol-functionalized polymer ligands. The particle size and size distribution was controlled by subtle variation of the polymer structure. It was shown that poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were the most effective stabilizing polymers in the group studied and that relatively low molar mass ligands (approximately 2500 g/mol) gave rise to the narrowest particle size distributions. Particle uniformity and colloidal stability to changes in ionic strength and pH were strongly affected by the hydrophobicity of the ligand end group. "Multidentate" thiol-terminated ligands were produced by employing dithiols and tetrathiols as chain-transfer agents, and these ligands gave rise to particles with unprecedented control over particle size and enhanced colloidal stability. It was found throughout that dynamic light scattering (DLS) is a very useful corroboratory technique for characterization of these gold nanoparticles in addition to optical spectroscopy and TEM.

Avidin↗
PubMed2006

Formation of spherical nanostructures by the controlled aggregation of gold colloids.

Stable suspensions of size-uniform spherical assemblies of 5-8 nm gold colloids in toluene are readily obtained by cross linking the colloidal particles using alkanedithiols within a defined range of gold-dithiol molar ratios. The assemblies are very stable and remain suspended in toluene for several months without significant aggregation. These porous gold spheres can be further organized into hierarchically assembled relatively linear chains by the addition of ethanol.

Gold Colloid↗
PubMed2005

In situ crystallization of low-melting ionic liquids.

Single crystals of five very low-melting ionic liquids, [emim]BF4 (mp -1.3 degrees C), [bmim]PF6 (+1.9 degrees C), [bmim]OTf (+6.7 degrees C), [hexpy]NTf2 (-3.6 degrees C), and [bmpyr]NTf2 (-10.8 degrees C), have been grown using a combined calorimetric and zone-melting approach and their crystal structures determined by X-ray diffraction.

Journal Article↗
PubMed2005

Aligned porous materials by directional freezing of solutions in liquid CO2.

We report here a method for generating structures with aligned macropores by templating solidified carbon dioxide. The CO2 template phase can be removed by direct sublimation to yield a dry, solvent-free porous material that may be useful in applications such as tissue engineering and aligned cell growth.

Journal Article↗
PubMed2005

Aligned two- and three-dimensional structures by directional freezing of polymers and nanoparticles.

The preparation of materials with aligned porosity in the micrometre range is of technological importance for a wide range of applications in organic electronics, microfluidics, molecular filtration and biomaterials. Here, we demonstrate a generic method for the preparation of aligned materials using polymers, nanoparticles or mixtures of these components as building blocks. Directional freezing is used to align the structural elements, either in the form of three-dimensional porous structures or as two-dimensional oriented surface patterns. This simple technique can be used to generate a diverse array of complex structures such as polymer-inorganic nanocomposites, aligned gold microwires and microwire networks, porous composite microfibres and biaxially aligned composite networks. The process does not involve any chemical reaction, thus avoiding potential complications associated with by-products or purification procedures.

Anisotropy↗
PubMed2005

Functional oligo(vinyl acetate) CO2-philes for solubilization and emulsification.

The development of inexpensive and biodegradable CO2-soluble ligands, surfactants, and phase transfer agents is an important goal in the implementation of supercritical fluid technology. We report here a potentially generic synthetic route to inexpensive oligo(vinyl acetate) CO2-philes for applications such as solubilization and emulsification. These materials are shown to outperform more expensive fluorinated surfactants in particular applications.

Acetates↗